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  • 1
    Language: English
    In: Geoderma, 01 July 2019, Vol.345, pp.63-71
    Description: Soil structure is not static but undergoes continuous changes due to a wide range of biotic and abiotic drivers such as bioturbation and the mechanical disturbance by tillage. This continuous alteration of soil structure beyond the pure swelling and shrinking of some stable structure is what we refer to as soil structure dynamics. It has important consequences for carbon turnover in soil as it controls how quickly soil organic matter gets occluded from or exposed to mineralization. So far there are hardly any direct observations of the rate at which soil pores are formed and destroyed. Here we employ are recently introduced labeling approach for soil structure that measures how quickly the locations of small garnet particles get randomized in soil as a measure for soil structure dynamics. We investigate the effect of desiccation crack dynamics on pore space attributes in general and soils structure turnover in particular using X-ray microtomography for repeated wetting-drying cycles. This is explored for three different soils with a range of soil organic matter content, clay content and different clay mineralogy that were sieved to a certain aggregate size fraction (0.63–2 mm) and repacked at two different bulk density levels. The total magnitude of desiccation crack formation mainly depended on the clay content and clay mineralogy. Higher soil organic matter content led to a denser crack pattern with smaller aperture. Wetting-drying cycles did not only effect visible macroporosity (〉8 μm), but also unresolved mesoporosity. The changes in macroporosity were higher at lower bulk density. Most importantly, repeated wetting-drying cycles did not lead to a randomization of distances between garnet particles and pores. This demonstrates that former failure zones are reactivated during subsequent drying cycles. Hence, wetting-drying resulted in reversible particle displacement and therefore would not have triggered the exposure of occluded carbon that was not already exposed during the previous drying event.
    Keywords: Soil Structure ; Desiccation Cracks ; X-Ray Tomography ; Macropores ; Clay Mineralogy ; Carbon Turnover ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 2
    Language: English
    In: Geoderma, 15 December 2018, Vol.332, pp.10-19
    Description: There is a long-lasting debate about the effects of tillage practices on soil structure and structure-mediated ecosystem properties like hydraulic conductivity and crop productivity. This is investigated in a long-term field experiment on tillage practices at the Westerfeld trial in Bernburg, Germany (25 years of different management). Here we combine soil structure information obtained by X-ray microtomography with bulk properties like bulk density, air capacity and saturated hydraulic conductivity, as well as integrative, ecological properties like earthworm abundance and crop yield. This study goes beyond previous studies in that the soil microstructure is investigated in two different depths, within (13–23 cm) and underneath (28–38 cm) the plow horizon. Furthermore the microstructure is investigated at two different resolutions (60 μm and 20 μm) by employing a nested sampling design. The plowed horizon in the conventional tillage plots differs from the undisturbed soil underneath the cultivator depth (13–23 cm) in the reduced tillage plot by lower bulk density, higher air capacity, higher saturated hydraulic conductivity, higher macroporosity and pore connectivity. After 25 years of reduced tillage saturated hydraulic conductivity only marginally recovered in the abandoned plow pan (28–38 cm). Macropore density and connectivity did not change significantly as compared to the current plow pan under conventional tillage. The topsoil underneath the cultivator depth in the reduced tillage plot developed a “no-till pan”, as porosity and pore connectivity where smaller than in greater soil depths. Image-based macroporosity and laboratory-based air capacity showed good agreement. Overall, the combination of hydraulic measurements and X-ray CT imaging of soil microstructure at different resolutions provides a comprehensive view on soil structure modification by tillage practices. The change from conventional to reduced tillage led to a compaction of soil that was not compensated by higher bioturbation as reported for other sites. This is explained by unfavorable conditions for anecic earthworms (frequent dry periods with severely impaired penetrability of the loess substrate) as well as the absence of very deep rooting, perennial crops in crop rotation.
    Keywords: Tillage Effects ; X-Ray Tomography ; Conservation Agriculture ; Macroporosity ; Saturated Hydraulic Conductivity ; Plow Pan ; Earthworm Abundance ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 3
    Language: English
    In: European Radiology, 2017, Vol.27(8), pp.3244-3248
    Description: To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s00330-016-4684-9 Byline: Julius Matthias Weinrich (1), Roland Diel (2), Markus Sauer (1), Frank Oliver Henes (1), Karen Meywald-Walter (3), Gerhard Adam (1), Gerhard Schon (4), Peter Bannas (1) Keywords: Tuberculosis screening; European refugee crisis; Epidemiology; Pulmonary tuberculosis; Chest X-ray Abstract: Objective Our aim was to determine the prevalence of tuberculosis (TB), the number needed to screen (NNS), and the diagnostic accuracy of chest X-ray (CXR) screening to detect active pulmonary TB during the 2015 European refugee crisis. Materials and methods We evaluated data of all refugees who underwent CXR screening in a single-centre of one German metropolitan area in 2015. We determined the prevalence of TB, NNS, and accuracy of CXR to detect active pulmonary TB. Reference method for active TB was the database of all definite TB cases registered at the Department of Public Health. Results A total of 17,487 immigrants underwent single-centre CXR screening in 2015 prevalence of definite pulmonary TB was 0.103%. The NNS for detecting one case of active pulmonary TB was 1749. CXR had a sensitivity of 55.6% [95% confidence interval (CI) 30.8--78.5%) and a specificity 98.3% (CI 98.1--98.5%) to reveal one case of active TB. Conclusion Our single-centre study indicates that chest X-ray screening for TB during the 2015 European refugee crisis was of low yield due the low prevalence of TB and high number needed to screen, thus implicating the need for improved screening algorithms adapted to the overwhelming number of refugees. Key Points acents Prevalence of pulmonary tuberculosis (TB) among refugees in 2015 was low (0.103%). acents The number needed to screen to detect one case of active pulmonary TB was 1749. acents Tuberculosis X-ray screening resulted in a low sensitivity and high specificity. acents Tuberculosis X-ray screening during the European refugee crisis is of low yield. acents Improved screening algorithms are needed due to the overwhelming the number of refugees. Author Affiliation: (1) Department of Diagnostic and Interventional Radiology and Nuclear Medicine, University Medical Center Hamburg-Eppendorf, Martinistra[sz]e 52, 20251, Hamburg, Germany (2) Institute for Epidemiology, University Medical Hospital Schleswig-Holstein, Airway Research Center North (ARCN), Kiel, Germany (3) Public Health Department Hamburg Central, Hamburg, Germany (4) Department of Medical Biometry and Epidemiology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany Article History: Registration Date: 29/11/2016 Received Date: 30/08/2016 Accepted Date: 29/11/2016 Online Date: 03/01/2017
    Keywords: Tuberculosis screening ; European refugee crisis ; Epidemiology ; Pulmonary tuberculosis ; Chest X-ray
    ISSN: 0938-7994
    E-ISSN: 1432-1084
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  • 4
    Language: English
    In: mBio, 30 July 2013, Vol.4(4)
    Description: In infection experiments with genetically distinct Mycobacterium tuberculosis complex (MTBC) strains, we identified clade-specific virulence patterns in human primary macrophages and in mice infected by the aerosol route, both reflecting relevant model systems. Exclusively human-adapted M. tuberculosis lineages, also termed clade I, comprising "modern" lineages, such as Beijing and Euro-American Haarlem strains, showed a significantly enhanced capability to grow compared to that of clade II strains, which include "ancient" lineages, such as, e.g., East African Indian or M. africanum strains. However, a simple correlation of inflammatory response profiles with strain virulence was not apparent. Overall, our data reveal three different pathogenic profiles: (i) strains of the Beijing lineage are characterized by low uptake, low cytokine induction, and a high replicative potential, (ii) strains of the Haarlem lineage by high uptake, high cytokine induction, and high growth rates, and (iii) EAI strains by low uptake, low cytokine induction, and a low replicative potential. Our findings have significant implications for our understanding of host-pathogen interaction and factors that modulate the outcomes of infections. Future studies addressing the underlying mechanisms and clinical implications need to take into account the diversity of both the pathogen and the host. Clinical strains of the Mycobacterium tuberculosis complex (MTBC) are genetically more diverse than previously anticipated. Our analysis of mycobacterial growth characteristics in primary human macrophages and aerogenically infected mice shows that the MTBC genetic differences translate into pathogenic differences in the interaction with the host. Our study reveals for the first time that "TB is not TB," if put in plain terms. We are convinced that it is very unlikely that a single molecular mechanism may explain the observed effects. Our study refutes the hypothesis that there is a simple correlation between cytokine induction as a single functional parameter of host interaction and mycobacterial virulence. Instead, careful consideration of strain- and lineage-specific characteristics must guide our attempts to decipher what determines the pathological potential and thus the outcomes of infection with MTBC, one of the most important human pathogens.
    Keywords: Macrophages -- Microbiology ; Mycobacterium Tuberculosis -- Genetics ; Tuberculosis, Pulmonary -- Microbiology ; Virulence Factors -- Genetics
    E-ISSN: 2150-7511
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